Cook Islands. Year of the Snake, 4 Coin Set, 2013. Colored Proof Silver, Perth Mint Box & COA. Each of the four legal-tender proof coins in this set were struck from one ounce of .999 fine silver. The four designs on the reverse represent depictions of the Blue-lipped Sea Krait, the Yellow Banded Wolf Snake, the Red Bamboo Rat Snake and the Chinese Green Tree Viper.